The invention relates to an assembled shaft element, in particular an assembled camshaft for valve-controlled internal combustion engines, and to a method for making an assembled shaft element.
For internal combustion engines with variable valve control and/or shut down of individual cylinders, structures are known having cams or cam pairs that are axially movable on the shaft and which, for example, carry two different cam contours per poppet valve and thus cause different control times when being switched. If one of the contours has a circular symmetry (cam base circle), the poppet valve can also be shut down. When combining such “switching cams” with non-switchable fixed cams, both variants have to be built as assembled version for mounting reasons alone, for example via a splined tooth system, which is easy to mount while ensuring a reliable transmission of the drive torque and an adequate support of the occurring alternating torques. Since for example such a splined tooth system has play, significant noise emissions can occur during engine operation. These noise emissions are caused in particular by the alternating torque which acts on the splined tooth system and is caused for example by valve and pump cams.
DE 197 10 847 C2 and DE 37 17 190 A1 both already disclose to push cam-bearing hub base bodies onto a shaft in a material-removing manner. Such a connection however, has the disadvantage that the chip formation decreases the transmittable torque, because material is broken out of the joining gap and can therefore no longer contribute to the formfit or the tension build up and thus to the force fit.
To avoid the latter, EP 1 741 945 A1 proposes to form a hub body recess that has a circular cross section and an absolutely smooth recess surface. The shaft which is to be connected to the hub body is widened in the connection area by a special knurling process to such a radius that elevations and depressions form on the outside of the shaft. To connect the two components, the hub body is pushed over the area of the shaft which has been widened by the knurling process and thus forms a force-fitting and formfitting connection with the shaft. This shaping however poses the risk of formation of cavities and thus tension losses which in turn can adversely affect the formfit and/or force fit between the shaft and the hub body.